The invention relates to differential pressure transducers. More specifically, the present invention relates to differential pressure transducers for gas turbine motors.
For purposes of monitoring or controlling driving gears driven by gas turbine motors, it is advantageous if pressure differentials can be reliably measured at specific locations, particularly in the fuel and lubricating oil systems. It is problematic to measure pressure differences with available pressure transducers, such as barometric cells, due to weight, cost and reliability factors.
The barometric cells typically consist of an evacuated vessel with an elastically deformable membrane. Variable electrical signals are generated by mechanical deformation of the membrane and an electrical change of resistors in a bridge circuit. It is possible to utilize these signals as a measure of differential pressures. However, the high fuel and oil temperatures in gas turbine motors as well as the pressure peaks in these fluids produce a very poor reliability of the barometric cells. Also, barometric cells have problems due to undetectable deformations of the critical elements (membrane, resistors). Because of these disadvantages, barometric cells have not been successfully applied in motors.
Differential pressure monitors for motors have made use of pressure-controlled electrical switches according to the yes/no principle. The yes/no electrical switches have mechanical spring elements that snap between two end positions. The switches have insufficient pressure monitoring and fail to detect the development of a differential pressure. Accordingly, the yes/no electrical switches exhibit problems in measuring and detecting pressure differentials.
For position measurement under difficult conditions, the linear variable displacement transducer (LVDT) principle is known. This is a matter of electrical position pickups or displacement sensors having an at least approximately linear dependency between a signal and a path. As is well known, these sensors are also suitable for high temperatures and heavier mechanical loads.
The present invention provides new differential pressure transducers. In particular, the present invention provides new differential pressure transducers for gas turbines driving gears, motors, or thrusters, for example. The differential pressure transducers for gas turbines measure variable pressure differences within a medium or between different mediums.
In an embodiment, a differential pressure transducer for gas turbine motors is provided for measuring variable pressure differences inside a medium or between different media, particularly for use in contact with hot media such as the fuel, the lubricating oil, and the process gas. The differential pressure transducer is implemented as a linear displacement sensor accordingly to the linear variable displacement transducer (LVDT) principle and has a piston-type core of ferromagnetic material that is bounded within a housing, can be moved axially, and being at least approximately fluid-tight. At least one spring element determines an axially set position of the core given a nominal differential pressure. The differential pressure transducer also has a primary coil having a terminal for an electrical alternating voltage in which the coil extends coaxial to the core approximately over its stroke range, and two identical secondary coils that are separately voltage-tapped, in which the coils are arranged in succession axially, extend together approximately over the length of the primary coil and being coaxial thereto. A tubular housing with a respective delivery connection on either side of the stroke area of the core is also provided.
In an embodiment of a differential pressure transducer, the primary coil and the secondary coils are arranged on the outside of the tubular housing.
In an embodiment of a differential pressure transducer, the primary coil and the secondary coils are arranged on the inside of the tubular housing, and the coils are embedded in a coil body that is itself tubular, which leads the core in its interior such that it can be moved axially.
In an embodiment of a differential pressure transducer, there is a parallel connection, in terms of flow, to a line having a fixed or displaceable choke element, for example having a diaphragm or a valve, whereby a delivery connection empties into the line upstream of the choke element. Another delivery element empties into the line downstream of the choke element. The core is lead such that it is not entirely sealed in terms of fluid and has a defined leakage gap at its perimeter.
In an embodiment of a differential pressure transducer for differential pressure measurement between different media, the core is led (moved) so as to be hermetically sealed. For example, the hermetic seal may be by a roll stocking seal.
In an embodiment of a differential pressure transducer, there is a pressure spring between the core and the housing on the side of the core that is loaded by the lower operating pressure.
One advantage of the present invention is to provide differential pressure transducers for gas turbine motors that enables the continuously adjustable measuring of variable pressure differences within a medium or between different media and that also functions reliably in the long term even under the harsh conditions present in motors. The differential pressure transducers provide an electrical differential pressure signal that is substantially proportional to the differential pressure.
Other advantages and objects of the present invention will become apparent upon reading this disclosure, including the appended claims and with reference to the accompanying drawings. All of the advantages and objects of the present invention may be desired, but may not necessarily be required to practice the present invention.